Ratio & Proportion (Railway Maths) (Part – IV)

Total Questions: 50

31. Find the smallest of three positive numbers if the numbers are in ratio of 3 : 7 : 8 and the sum of their squares is 7808. [RRB NTPC 01/02/2021 (Morning) ]

Correct Answer: (b) 24
Solution:

Let, The Ratio of the number = 3x : 7x : 8x Sum of their squares
= (3x)² + (7x)² + (8x)² = 7808
⇒ (9 + 49 + 64)x² = 7808
⇒ 122x² = 7808 ⇒ x = 8
Now, smallest number = 3 × 8 = 24

32. What is the compound ratio of 45 : 75, 3 : 5, 51 : 68 and 256 : 81 ? [RRB NTPC 01/02/2021 (Evening) ]

Correct Answer: (a) 64/75
Solution:

33. If a : b :: 3 : 4 then the value of expression 5a - 3b / 7a + 2b is: [RRB NTPC 01/02/2021 (Evening) ]

Correct Answer: (a) 3/29
Solution:

34. The speeds of three trains are in the ratio 2 : 3 : 5 . The amount of time taken by these trains to travel the same distance is in the ratio : [RRB NTPC 02/02/2021 (Morning) ]

Correct Answer: (a) 1/2 : 1/3 : 1/5
Solution:

If distance is equal, the ratio of time is opposite to the ratio of speed. Ratio of time = 1/2 : 1/3 : 1/5

35. If x : y = 4 : 3, then the value of x³ - y³ : x³ + y³ is: [RRB NTPC 04/02/2021 (Morning) ]

Correct Answer: (d) 37 : 91
Solution:

36. 35% of a number is the same as 30% of another number. Find the ratio of the first number to the second number. [RRB NTPC 04/02/2021 (Evening) ]

Correct Answer: (b) 6 : 7
Solution:

37. The sum of two numbers is 80 and their difference is 8. The ratio of the first number to the second number will be? [RRB NTPC 04/02/2021 (Evening)]

Correct Answer: (a) 11 : 9
Solution:

38. John, Sarah, Tom and Joane bought 3 pizzas of the same size in all. John ate 2/4 of a pizza. Sarah, Tom and Joane ate 3/4 of a pizza each. How much pizza was left? [RRB NTPC 05/02/2021 (Morning)]

Correct Answer: (b) 1/4 of a pizza
Solution:

39. Rs 110 are contained in a box which consist of one rupee, 50 paise and 25 paise coins in the ratio 1 : 2 : 3 . What is the number of 50 paise coins ? [RRB NTPC 08/02/2021 (Morning) ]

Correct Answer: (c) 80
Solution:

40. How much should we add to each of 7 and 9 so that the ratio of the two numbers thus formed is 13 : 14. [RRB NTPC 08/02/2021 (Morning) ]

Correct Answer: (b) 19
Solution: